{The children of the promise} (	a tekna t(8873) epaggelias).
Not through Ishmael, but through Isaac. Only the children of the
promise are "children of God" (	ekna tou theou) in the full
sense. He is not speaking of Christians here, but simply showing
that the privileges of the Jews were not due to their physical
descent from Abraham. Cf.  Lu 3:8 .